I want to completely non invasively determine the characteristics of a 
metal surface.
(The nozzle, chamber and injector surfaces of a 50 year old "Corporal" 
liquid fuel rocket motor).
The aim is to produce a convincing report on the best way to conserve 
the equipment without actually "interfering" with it in any way.

I'd like to do this as cheaply and easily and quickly as possible (of 
course)(choose any 3).

Historical documents suggest that the material is Chromium plated mild 
steel but it may be a stainless steel and may be something else.

The nozzle has been painted at date unknown with paint or other paint 
like substance with surface-preparation unknown.

I need to know as best I may what each of the components is made of.
Any investigation *** MUST *** not only be wholly non-invasive but 
must be subsequently be able to be seen by the technically relatively 
uniformed to be non invasive. eg not only must I not scratch the paint 
work or metal surfaces but there must be no suspicion that that is 
what I really did. The reality is that it would almost certainly not 
matter if I did and that that may turn out to be a sensible and most 
effective method to use **** BUT **** it is not an option.

The equipment concerned is on loan from "The Smithsonian". I suspect 
they wouldn't care too too much if sensible tests were made BUT for 
local reasons, this is not an option.

The injector plate is unpainted and has a shiny "chrome" finish. (And 
it is almost certainly chromium plated).

Now, I KNOW that people will now suggest invasive methods, but any 
comments on non-invasive methods would be welcome.

I can look elsewhere and I have some ideas but there are often OTS / 
OTW / well,-fancy-that answers from this list, so ... .

- I intend to try examining the effect on the inductance of a coil 
placed with a pole face against the surfaces. Various frequencies may 
produce differing results but I'm unlikely to get that fancy. (eg at 
high enough frequencies the skin effect would be confined to the very 
surface layer and a thin chromium layer may have more effect than at 
low frequencies.)

- Use of a permanent magnet SHOULD rapidly allow a mild steel / 
stainless steel test. (Some stainless steels do exhibit ferro-magnetic 
properties but the ones possibly used here probably don't).

- Conduction of a heat pulse may help. Maybe not on the painted 
surfaces. (An excellent way of differentiating between diamond and 
cubic zirconium).


            Russell



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